Influence of Snow Patches and Snow Avalanches on the Alpine Treeline Ecotone

Snow avalanches, snow accumulation, and snow ablation patterns were mapped and analyzed to assess their impacto n the three-dimensionapl osition,c omposition( closed canopy forest, open canopy forest, meadow, krummholz, and non-vegetated surfaces), and spatial structure of the Alpine Treeline Ecotone (ATE) in a portion of Glacier National Park, Montana,U SA. MultitemporaLl andsatM ultispectralS canner data were processed to derive snow accumulation and ablation patterns throughout a snow season. Landsat Thematic Mapper data were processed and combined with aerial photo interpretationsf or discerninga ndc haracterizingsn ow avalanchep aths. Transition matrices were used to assess the change in the state of snow cover conditions, whereas multiple regression analyses were used to examine the position and character of snow avalanche paths. The analyses were framed and implemented within a geographic information system (GIS) approach. Results indicate a snowmelt pattern progressing from zonal to azonal; influence of local site and situation factors in snow accumulation and ablation patterns; and the importance of topography, geologic structure, and lithology in defining the starting elevation and source area of snow avalanche paths. Finally, a conceptual process is presented where sites affected by stresses and disturbances are analyzed at a local spatial scale for analysis through a deterministic model, whereas regionals tressesa ndd isturbancesa rea ssessed throughr emote sensing and GIS approaches for analysis through empirical models.